Clemens A. Heusch

The A dependence of the nuclear structure function ratios

Results are presented for six nuclei from Be to Pb on the structure function ratios F-2(A)/F-2(C)(X) and their A dependence in deep inelastic muon scattering at 200 GeV incident: muon energy. The data cover the kinematic range 0.01 < x < 0.8 with Q(2) ranging from 2 to 70 GeV2. The A dependence of nuclear structure function ratios is parametrised and compared to various models.

Measurement of the inclusive decay properties of charmed mesons

Abstract We report a high statistics study of the inclusive decay properties of the charmed D0 and D+ mesons, and the first inclusive study of the charmed Ds+. The data are collected at s =3.77 GeV and s =4.14 GeV with the Mark III detector at the e+e− storage ring SPEAR. For each charmed meson species, the charged-particle multiplicity, the strangeness content of the final state, and the average π0 multiplicity are determined.

Measurement of the neutron and the proton F2 structure function ratio

The ratio of the structure function F2n/F2p (x) has been measured in deep inelastic scattering of 274 GeV muons on hydrogen and deuterium targets exposed simultaneously to the beam. The results were obtained from 0.3 (0.6) million events from hydrogen (deuterium) in the range 0.004 <x< 0.8 and 1 <Q2< 190 GeV2. At x < 0.25 both the statistical and the systematic error is below 2%. Implications for parton distributions and for the σw/σz production cross section ratio in pp collisions are discussed. When compared to other results obtained at lower energies, the data indicate a Q2 dependence of the ratio.

Lepton-flavour violation induced by heavy Majorana neutrinos

Abstract We investigate the reaction e−e−→W−W− in the center-of-mass energy regime far above threshold for W-pair production. We assume lepton-flavour violation to be mediated by a Majorana mass matrix for six neutrino flavours as is natural in SO(10) assignments. We show that the cross section compatible with constraints from low energy may well be detectable at √s=0.5 TeV under conservative assumptions on neutrino mixing angles and masses. The dependence on center-of-mass energy α(√s)4 may thus lead to sizable rates at 1–2 TeV.

Ratio of J/Psi production cross sections in deep inelastic muon scattering from tin and carbon

We present results on J/ψ production in muon interactions with tin and carbon targets at incident muon energies of 200 and 280 GeV. The ratio of cross sections per nucleon for J/ψ production on tin and carbon, R(Sn/C), is studied as a function of pT2, z and x. We find an enhancement for coherent J/ψ production Rcoh(Sn/C) = 1.54 ± 0.07, a suppression for quasielastic production Rqe(Sn/C) = 0.79 ± 0.06 and for inelastic production Rin(Sn/C) = 1.13 ± 0.08. The inelastic cross section ratio can be interpreted within the Colour Singlet model as an enhancement of the gluon distribution in tin with respect to that in carbon. The dependence of the ratio on z and pT2 can explain the discrepancy between the results obtained in previous experiments.

A study of the reaction p+d → 3He+π0 in the resonance region☆

Abstract The reaction p + d → 3 He + π 0 was studied at incident proton energies of 377, 462 and 576 MeV. A comparison of our data with others suggests the existence of a sharp forward peak in θ He at 377 and 462 MeV, which is unexplained by the theory and disappears at higher energies.

Precision-measurement of Structure-function Ratios For Li-6, C-12 and Ca-40

The structure function ratiosF2C/F2Li,F2Ca/F2Li andF2Ca/F2C were measured in deep inelastic muonnucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085<x<0.6 and 0.8<Q2<17GeV2. The sensitivity of the nuclear structure functions to the size and mean density of the target nucleus is discussed.

Direct measurements of the thermal conductivity of various pyrolytic graphite samples (PG,TPG) used as thermal dissipation agents in detector applications

We performed model measurements on heat conduction in graphite-based structures, using several configurations. We describe our method for the direct measurement of thermal conductivity both in-plane and out-of-plane, for TPG and PG samples. Our results for the in-plane thermal conductivity coefficient, Kab were obtained with two different sets of boundary conditions; they are in good mutual agreement. Those for the transverse coefficient, Kc; differ by a significant factor from the values published by the producers of the material. r 2002 Elsevier Science B.V. All rights reserved.

A strategy for discovering heavy neutrinos

Abstract We discuss collisions of two equally charged leptons l − l − or l + l + , with l = e , μ , where the exchange of heavy neutrino flavors induces the lepton-flavour-violating transitions to a pair of equally charged gauge bosons, W − W − or W + W + . In the center-of-mass energy region well above W pair production threshold, but below the heavy neutrino mass, acceptable mass and mixing parameters for the heavy neutrino flavor lead to cross sections of a size and energy dependence that permit a clear detection of lepton flavor violation; the resulting signal constitutes a unique discovery channel for TeV-level Majorana neutrinos.

A large-solid-angle spectrometer for high-energy electrons and photons

Abstract We describe the design and performance characteristics of a 1.5 × 1.5 m2 detector which measures electron and photon trajectories and energies in the energy range 10–200 GeV. The position resolution is σ≌3 mm in each transverse coordinate for isolated single showers. The energy resolution is σ E /E = 20 E − 1 2 % . Neighboring showers separated by more than ∼12 cm in one coordinate are resolved for π0, η0, ω0, … decay recognition.